2025 – PAGE 167 – NEONATOLOGY

2025 – Core Study Guide 07 –Neonatology 2025 – PAGE 167 – NEONATOLOGY

HEAD CIRCUMFERENCE – MACROCEPHALY, HYDROCEPHALY, AND MICROCEPHALY

To know if you’re dealing with possible macrocephaly, hydrocephaly, or microcephaly, you first have to know what a baby’s head circumference should be. A normal newborn’s head circumference is approximately 35 cm. After that, expect the head circumference to increase by 1 cm/month for 6 months and then ½ cm/month from 6−12 months.

PEARL: 50th Percentile for HC at birth is 35 cm. For a child born with a head circumference of 35 cm, head circumference should increase to 44 cm at one year of age.

  • MACROCEPHALY: > 97 percentile for age, though the history will usually include a normal HC at birth. If the child’s development is in fact normal, just measure the parents’ heads to see if it is FAMILIAL MACROCEPHALY!
    • PEARL: If there are developmental issues or other issues with the child, HYDROcephaly is likely the main problem.
  • HYDROCEPHALY: Look for a BIG HEAD AT BIRTH + NEUROLOGIC ISSUES.
    • PEARL: Large anterior fontanelles are found in both macrocephaly and hydrocephaly. The finding is very nonspecific. If the ABP mentions a BULGING FONTANELLE, think HYDROCEPHALY.
    • PEARL: Neither macrocephaly nor hydrocephaly result in papilledema. Both of these conditions are usually due to slow processes, and papilledema is usually the result of an ACUTE problem.
  • MICROCEPHALY: HC is usually normal at birth (~35 cm) and then falls off the curve.

NUTRITION, BREAST MILK, & FORMULA

NEONATAL POTASSIUM REQUIREMENTS

Neonatal potassium requirements are 2 mEq/kg/day.

NEONATAL SODIUM REQUIREMENTS

Neonatal sodium requirements are 3 mEq/kg/day.

PROTEIN INTAKE

High protein intake can result in a high osmotic load. The osmotic load is affected by chloride, phosphorus, potassium, and sodium (NOT calcium). High osmotic loads can result in fluid losses, renal impairment, and weight loss.

  • FULL TERM BABY: 2–2.5 g/kg/day for the first 6 months of life
  • PREMATURE BABY: 3.5 g/kg/day. Premature babies have higher protein requirements in order to avoid a negative nitrogen balance (which can result in weight loss).
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